1. Field of the Invention
The present invention relates to a field emission lamp (FEL), and more particularly, to an FEL having a fast response time capable of being used as a backlight unit of a liquid crystal display device.
2. Discussion of Related Art
Liquid crystal display (LCD) devices provide a voltage to each pixel in a liquid crystal panel according to an input image signal to display images by controlling light transmission of the pixels, and are generally used in laptop computers, desktop computers, LCD-TVs and mobile communication terminals.
Color display methods of LCD devices are classified into a space division method of displaying various colors by spatially mixing spatially divided pixels having unit colors (e.g., red, green and blue (RGB)), a color sequential driving method of displaying various colors by temporally mixing unit colors expressed sequentially, and a field sequential color driving method.
Here, in the color sequential driving method, a total frame on a liquid crystal panel is separated into sub-frames of a unit color (e.g., RGB), and backlight units include a single color light source of a unit color, respectively. Accordingly, when unit color lights are sequentially turned on for a short time, the unit colors may be temporally mixed together, thereby expressing various colors without color filters.
Conventionally, as the backlight unit of the LCD device, a cold cathode fluorescent lamp (CCFL) or light emitting diode (LED) has generally been used.
However, the CCFL causes environmental contamination because of the use of mercury (Hg) gas, has low response time and color reproduction, and is not suitable to making a panel lighter, thinner, shorter and smaller.
The LED is eco-friendly, compared to the CCFL. However, when a large amount of LEDs are used to increase light intensity, the production cost and heat may increase. In addition, although the LED has a faster response time compared to the CCFL, it is not enough to prevent color breaking occurring in the color sequential driving method.
Meanwhile, recently, local dimming, which is a technique to individually control a backlight unit, has been proposed. According to the local dimming technique, a backlight unit is selectively turned off at a dark side of an image, thereby reducing power consumption, increasing contrast ratio and reducing afterimages.
To apply such a local dimming technique to LCD devices, several hundreds of backlight units are needed. Thus, when LEDs are used as the backlight units, as described above, the production cost and heat increase.